1. Field of the Invention
This invention relates to endless coated abrasive articles and to their method of manufacture. In particular, the invention relates to so-called "spiral wound abrasive belts".
2. Description of the Prior Art
Endless coated abrasive articles, such as belts, sleeves, tubes, and the like, are used in a variety of abrading operations thus requiring that such be made and supplied by the coated abrasive manufacturer in a large variety of widths and circumferences.
Coated abrasive belts in most instances are only as wide as the coated abrasive material from which they are manufactured. In the manufacture of these belts, a piece of coated abrasive material, equal in width to the desired belt width, is cut at a suitable angle to its longitudinal direction. In a direction lengthwise, a length equal to the desired belt circumference plus an allowance for forming a lap joint, if such a joint is to be formed, is measured off. A second cut is then made at the same angle as the first. To at least one of the cut ends, after skiving, adhesive composition is applied and the ends are then joined by overlapping and are caused to adhere to one another by means well known to those skilled in the art. Alternatively, the piece of coated abrasive material may be cut to length without the allowance for overlap and the cut ends are butted and joined to one another with an overlapping reinforcing flexible patch suitably adhered to the backside of the two ends of the abrasive material.
This manner of abrasive belt manufacture, as one can readily observe, is limited in the maximum width of endless belt that can be manufactured to the maximum width of available coated abrasive material. Inherent apparatus limmitations in the coated abrasive industry, particularly in the coating apparatus, generally preclude the manufacture of coated abrasive material in widths greater than about 52 inches. However, the productin of steel sheets and the like in widths approaching 100 inches has created a demand for abrasive belts of equal or greater widths. Various attempts, as hereinafter more fully discussed, have been made to provide coated abrasive belts of a width greater than the width of conventionally available coated abrasive material. All of these attempts, to my knowledge, have met with only limited success.
According to one such above-mentioned methods of manufacture of "wider" belts, a piece of coated abrasive material of suitable width is cut at an angle to the length direction, as before. In a direction perpendicular to the cut edge the desired width of the belt is measured off and a second cut is made at the same angle as the first. A second piece is cut congruent with the first and the two pieces are joined along edges parallel with the length direction of the original coated abrasive material, either by forming an overlapping joint or by forming a reinforced butt joint in the manner previously described. By proper choice of width of coated abrasive material, angle of the cut with respect to the length direction of the coated abrasive material, and number of congruent pieces selected, wide, multiple-joint "sectional belts" covering a broad range of belt widths and belt circumferences can be fabricated. However, the necessity of fabricating multiple joints makes the manufacture of these "sectional belts" a relatively expensive process. Moreover, each additional joint in a belt is a potential additional source of belt weakening and a potential additional source of problem with process control and quality of workmanship.
Another method of manufacture of "wider" belts is the "patterned" sectional construction disclosed in Canadian Pat. No. 560,413, issued July 25, 1958, to S. E. Hill and H. N. Dyer, the latter inventor being the inventor in this application. The invention therein disclosed provides a method of manufacture of both sectional belts and single-joint belts, each having maximum strength and minimum stretch in its circumferential direction from a coated abrasive material having a relatively high strength and low stretch in one direction and a relatively low strength and high stretch in the perpendicular direction. Belts made according to this invention, however, have a large number of expensive joints and substantial waste is experienced in cutting the component parts to the required shapes.
Other methods of manufacture of endless "wider" belts and the like are also known. One such method involves winding an inner liner spirally on a mandrel having an outer circumference equal to the inside circumference of the desired abrasive belt, applying an adhesive to the outer surface of the inner liner, and winding spirally over the adhesive layer a strip of coated abrasive material. Such a method is widely used for the fabrication of belts in smaller sizes, up to, for example, 6 inches in diameter or 19 inches in circumference, but has not been found practical or is it widely used fo the fabrication of so-called "wide" belts.
Another method of manufacture of endless coated abrasive articles involving spiral winding is disclosed in Swiss Pat. No. 390,717. Therein an abrasive article of spiral configuration in which the edges abutt one another is disclosed. The joint thus formed is bridged with a metal band or thin synthetic resin film. A spiral would abrasive belt of slightly different configuration is disclosed in U.S. Pat. No. 2,189,754. The joint in the belt therein disclosed has overlapping beveled-edges.